In order to reduce the fuel consumption of vehicles and consequently the pollution which they generate, it is known to equip a vehicle with a micro-hybrid system, for example an alternator-starter, enabling a braking recovery mode.
Equally, a micro-hybrid system of the above type comprising a reversible electrical rotating machine, a reversible AC-DC voltage converter, an electric energy storage unit and a reversible DC-DC converter are known to the entity according to the invention.
The electric energy storage unit is formed from a plurality of very large capacitance condensers known as “super condensers”, “ultra-capacitors” or “UCAPs” by the person skilled in the art.
The electric energy recuperated by the electrical rotating machine is stored in the super condensers and is then returned for various uses, particularly to feed consumers with a floating DC voltage greater than the battery voltage.
Taking into account the nominal voltage levels actually available for the super condensers, it is known to mount the latter in series so as to form a pack of super condensers capable of supporting the voltage levels usually present in a micro-hybrid system with braking recovery as indicated above.
In this system, the disparities existing between the nominal voltage levels and capacitance values of the super condensers led the inventors to provide electronic balance circuits.
These electronic balance circuits have a primary function of protecting the super condensers against too high charge voltages able to cause voltage surges or premature ageing of the capacitor assembly, as well as against possible voltage inversions at the terminals of the super condensers which can have destructive consequences including on the electronic circuits connected to the terminals of the super condensers.
A certain homogeneity between the charge voltages of the various super condensers, facilitating the operation of the capacitor assembly, is achieved thanks to these balance circuits.
Thus, for example, if the vehicle is not used over long periods of time, the balance circuits continue to ensure symmetrical discharge from the pack of super condensers, ideally down to 0 V. Indeed, it is desirable that the pack of super condensers always remains balanced (especially with very low voltage) because, when the vehicle is restarted, the need to recharge the pack of super condensers as quickly as possible can have destructive consequences, on account of serious imbalances, if the discharge was not correctly followed through down to very low levels (2 V for example).
The introduction of balance circuits has therefore allowed technical progress in terms of reliability and life of the packs of super condensers.
Today, however, it is desirable to propose new solutions, on the one hand enabling the life of the capacitor assembly in the micro-hybrid system with braking recovery to be additionally increased and, on the other hand the possibilities of the capacitor assembly as a major component of the micro-hybrid system with braking recovery to be better utilized.